Heterocyclic Amine
Definition and meaning of Heterocyclic Amine in chemistry.
A heterocyclic amine is an organic amine in which the nitrogen atom is a member of a ring system (a heterocycle) rather than attached only to an open-chain carbon skeleton. The ring may be saturated, as in piperidine, or aromatic, as in pyridine and imidazole.
In more detail
Because the ring nitrogen's lone pair may occupy an sp3 orbital available for protonation or instead be delocalized into an aromatic pi system, heterocyclic amines range widely in basicity, strongly basic piperidine (pKaH about 11) contrasts with pyrrole, whose lone pair is locked into its aromatic sextet and is barely basic at all. This ring-embedded nitrogen motif is central to biochemistry: the purine and pyrimidine bases of DNA and RNA are heterocyclic aromatic amines, as are countless alkaloids and pharmaceutical drugs.
Key facts
| Field | Organic Chemistry |
|---|---|
| Defining feature | Ring nitrogen bears amine character |
| Common example | Pyridine, C5H5N |
| Biological role | Purine and pyrimidine bases of DNA/RNA |
Pyridine, a six-membered aromatic ring with one nitrogen replacing a CH unit, is a heterocyclic amine widely used as a base and solvent in organic synthesis.
Frequently asked questions
How does a heterocyclic amine differ from an aliphatic amine?
In a heterocyclic amine the nitrogen is itself a ring atom (part of the heterocycle), whereas in an aliphatic amine nitrogen is bonded to an open-chain carbon skeleton outside any ring.
Are the DNA and RNA bases heterocyclic amines?
Yes; adenine, guanine, cytosine, thymine, and uracil are all heterocyclic aromatic amines built on fused or single purine and pyrimidine ring systems.